How stone beer was brewed

It's only the last few centuries that metal kettles have become
something that most people could afford to own. So how did people brew
beer without a metal container to heat water in? One well-known
solution was to heat stones in a fire, and then throw them in the
liquid to be heated. I've written before about the
archaeology of brewing stones, but archaeology can't tell us how
people used the stones. So how did people actually brew with hot
stones?

Making some educated guesses

Let's consider what we can deduce from some fairly basic
understanding.

If you are going to brew beer, the one thing that you absolutely
must heat up is the mash. Unless you get the temperature up into the
60-70C range, the enzymes in the malt will not release the sugar in
the malts, and you will not be able to make beer.

You do not have to boil the wort. In fact, in the Nordic and Baltic
countries, many, perhaps even most, farmhouse brewers still don't boil
their wort. They brew raw ale.

Boiling the wort for an hour with hot stones is hard work.
Experimental archaeologist Merryn
Dineley reports that in some cases when reproducing ancient brews
she wasn't able to boil the wort at all.

Based on this, what you'd expect to find is that people in ancient
times used the hot stones to heat the mash, and didn't boil the wort
at all. Later, when they got metal kettles, they started just heating
water or juniper infusion and pouring it on the malts instead. Then,
some places they started boiling the wort, and other places they never
did. (This produced some interesting geographic
patterns.)

Copper kettle from Brå, Denmark, 3rd century BCE, Moesgaard Museum.

Looking at the documentation

As it turns out, there is substantial documentation on how stone
beer was brewed, so we don't need to guess.

Let's start with a favourite recipe of mine, published by Ola
Øyjorde in 1969. He grew up in Bøverdalen, one of the most remote
places in Norway. To get there you must travel all the way up
Gudbrandsdal, almost to where it ends in the mountains. Then, you take
a high side branch of the valley, one that goes past the two highest
mountains in Norway. That's Bøverdalen.

Øyjorde describes how his mother brewed. My guess is that he's
talking about the early 20th century. It's written in pretty heavy
dialect, but translated to English this is the key part:

The malts were poured into the mash tun and the filter was installed
in the strainer. Boiling juniper infusion was then poured into the
strainer, and sieved down into the mash tun. [This probably to
disinfect and clean the strainer.] Then the "gil stones", which had
been lying in the fire and turned glowing red, were added to the
mash tun to boil the mash. It was important to move the stones as
soon as they reached the bottom, so they didn't give a burned
flavour to the mash. For this they used the mash paddle. Then the
lid was placed on the mash tun, and the whole thing wrapped up so
that the mash could boil a while.[3]

That's the only thing the stones are used for.

(The term "gil" is the old word for the fermenter. I'm guessing the
stones are called that because the fermenter is probably the same
vessel as the strainer, and the stones are added to the strainer.)

Stone with mash stuck to it

This is interesting, and very much in line with what we deduced
above. But it's just one example, so it doesn't prove anything. But
what if we go through the entire recipe collection and look at every
single stone brewing recipe?

No

Place

Country

Year

Stones in mash

Wort boiled

1

Louhisaari

Finland

1780

Unclear

Unclear

2

Pakri

Estonia

1940

Yes

No

3

Bøverdalen

Norway

1969

Yes

Yes

4

Hollola

Finland

2007

Yes

No

5

Hunderup

Denmark

1941

Yes

No

6

Helsinge

Finland

1964

Yes

No

7

Sibbo

Finland

1964

Yes

No

8

Ossiach

Austria

1811

Yes

No

9

Sibbo

Finland

1958?

Yes

No

10

Klagenfurt

Austria

1906

Yes

No

11

Højst

Denmark

1941

Yes

No

12

Hjerkinn

Norway

1905

Yes

Yes

That's pretty definitive, I would say. As far as we can tell,
nobody used the stones in the wort, and just two recipes
definitely boiled the wort. And this is recipes from a huge area all
across Europe, all of them describing the brewing as it was in one
specific place.

In some cases people used hot iron rods or heated steel balls to
produce the same effect that you get from the hot stones[13].

What's also interesting is that as far as I can tell all of these
brewers had kettles. And as far as I can tell every single one added
hot water/infusion to the mash before turning to the stones. So they
didn't have to use stones. Why did they do it, then? A reason that's
repeated in many of these accounts is either that they wanted the dark
colour, or that they wanted the toasted flavour.

It doesn't appear in any of these accounts, but another trick
that's been reported in connection with hot stones is sprinkling them
with rye flour before adding them to the mash. Again the rationale is
to add colour and flavour.

At the SMÖF festival in Sweden Vykintas Motuza demonstrated stone
brewing as it was practiced until recently in Anykšiai in
Lithuania. He says that in that area people generally
make keptinis, where the malts are toasted in
the oven during brewing. But when they brew for weddings and other
occasions that require a lot of beer they don't have ovens large
enough to bake all the malts. In those cases they brew stone beer
instead, and use the stones to toast the malts.

During the brewing Vykintas deliberately held the stones in the top
layer of the mash with wooden tongs, slowly moving them around to
toast as much of the mash as possible.

Conclusion

Stone beer has obviously been brewed over most of northern Europe
in the past, but mostly died out when metal kettles became more
affordable. The timeline for the dying out is not clear at all, but in
remote areas it's clear that the practice continued into the present
day, and some places it's still alive. Interestingly, the motivation
seems to be mostly the flavour.

Brewing stones after use

Sources

I should add that when SERDE demonstrated
stone brewing in Latvia they also used the
stones in the mash. Ugis cited an interview with "a guy named Malti,
of all things," but it's not in their printed material, so I didn't
include it in the table above.

Hellenius's 1780 account of sahti brewing
also describes stones being used in the mash, but he doesn't cite any
specific place, so I haven't included it in my recipe database. There
are more descriptions of stone brewing from the Baltics that say the
same thing, but I'm leaving them out here for the same reason.

Similar posts

The small town of Aizpute, in western Latvia, is home to
SERDE, which calls itself an
"interdisciplinary art group." Their focus seems to be mostly art, but
they also study traditional culture, including traditional brewing

Related, surely, to the English word 'gyle', originally 'wort in the process of fermentation', later 'fermentatipon batch', from Middle Dutch 'gijl', from 'gīlen', to boil, ferment.

Lars Marius Garshol - 2016-12-18 09:42:44

I can't believe I didn't think of that myself! I'm no linguist, but, yeah, that sounds extremely plausible. It was "gil" in Old Norse, too. I'll have to look in an etymological dictionary to see if you're right.

Aaron - 2016-12-18 09:44:46

Great post! Another variable to expirament with!

Graham Dineley - 2016-12-18 16:30:23

Hi Lars, I'm greatly impressed by your work.
We have never tried boiling wort with hot rocks, as you say it is not worth the effort. I've always thought that boiling was a Hop thing, gruit doesn't need it. I have heard of Americans doing it for the "caramel flavour", but I think that was their misunderstanding.

we mashed with hot rocks. 200 litres of water and 50Kg of malt. One charge of rocks brought the trough up to blood heat. We recovered them by hand. Then the second charge brought it to strike heat. We covered it and left it, with the odd hot rock to keep the temperature up.
Once it had cooled enough to handle we collected about 30 litres off the clear top, and pitched bakers yeast on it when it had cooled to blood heat. Raw Ale.
Recovering a sensible amount of wort and sparging will be an interesting experiment. We had a ferry to catch!
As we were using meadowsweet flowers for gruit, 50gm, I added them after primary fermentation. I have known meadowsweet to inhibit primary fermentation.
Some people said it was good. I hear Lauren's Dad liked it.

Hello Lars,
I read some of your postings and find them quite inspiring for our project.
Would you allow us to translate some of your postings into German and repost them then on our blog? With proper mentioning of your credits of course.

We are a group of stone age brewers. In a swamp nearby wheat pollen was found in a layer from 6.000 b.c. Assuming this is early evidence of brewing grain we brew stone age beer (that is: mesolithic beer) without metal, nor hop, nor ceramics. Clearly that is stone beer.

And just as Graham I can confirm: It works fine. Our beer is sour, fruity and refreshing. (We also make hopped stone beer which resembles modern beer a lot more. It has a smokey taste to it and some claim to taste a little caramel. Throwing 650 °C-stones into sugar water (mesh) produces inevitably some caramel.)